A 2013 study by published in the New England Journal of Medicine (NEJM) has proposed a new link between eggs and coronary heart disease (CHD) that doesn’t involve cholesterol. A team of researchers, led by Dr. Stanley Hazen, showed that dietary choline – a nutrient found largely in eggs, beef liver, and other animal foods – is metabolized by bacteria in our gut and then converted by the liver into TMAO. They demonstrated this with a “choline challenge:” feeding volunteers two large hard-boiled eggs (with approximately 250 mg of choline each) along with 250 mg of supplemental choline that was tagged with a heavy isotope. The isotope acts like a chemical “label” that allowed the researchers to track what happened to the choline after it was ingested. Their data did indeed show an increase in both labeled TMAO and total TMAO (in urine and blood) in the volunteers after they consumed the eggs and supplemental choline.
Source: Choline and TMAO: Eggs still don’t cause heart disease